Torque regulator



JUL 2l 1947. s. I .fLlNDBl-:CK 2,414,539

TORQUE REGULATOR Filed June 16, 1943 v 77g. Z. ATTORNEY Patented Jan'. 21, 1947 UNITED STATES TORQUE REGULATOR Simon L. Lndbeck, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application J une 16, 1943, Serial No. 491,009

This invention relates to electric control means and more particularly to systems of control for limiting the torque on prime movers operating generators connected to operate electric motors.

One broad object of my invention is to control the excitation of a generator, having a relatively large motor connected thereto, in such a manner that large variations of load torque on the motor do not overload the prime mover operating the generator.

by a Diesel engine so that the speed on the Diesel engine can not fall below va given value.

Another object of my inventiony is the provvision of regulating the torque imposed on av Diesel engine by an alternating current gen-- lDuring this operation it is desirable to obtain as high a torque as is possible, limited only by the torque capacity. of the engines.

A still further object of my invention is the .provision of automatic, simple, cheap, and efficient means for limiting the torque output of Diesel engines to the highest values which the engines will sustain without falling below the' minimum permissible speed value.

Other objects of my invention will become more apparent from a study of the following speciiication'and the accompanying drawing, in which:

Figure lis a diagrammatic showing of a ship propulsion system using my invention; and

Fig. 2 is a showing of some curves for illustrating the novel features of my invention.

In Diesel-electric alternating current driven ships usually from one to eight Diesel engines Y are mechanically coupled'to as many alternators which together or any selected group supply energy to a single synchronous motor driving a propeller. There may, cf course, be several propellers per ship, in which case several groups of these unitsarev used. f

For convenience I show only three Diesel engines I, 2 and 3 driving respectively, the alternatorsll, and 6. The arrangement is such that the motor M- may be connected for either direction of operation by the reversing switch l. The motor is excited from a suitable source as shown 5 Claims. (Cl. 172-8) and the generator iield windings 9, I I and I3 may be selectively connected to the exciter E by the switches I5, Il and I9. The generators, or alternators, may be connected to the motor M in 5 any combination group by the switches.

In actual practice the arrangement of the switches so far mentioned is not as simple as I show them but suitable interlocking means are provided. For instance when switch 2| is closed,

, vswitch I5 should be in the position shown, and y Another more specific object of my invention is .j to control the excitation of an alternator driven .when switch 2`I is open the discharge resistor I0 should be connected to the field 9. A similar relation holds for switches I'I and 23 and discharge resistor I2, and switches I9, and 25 and discharge resistor I4.

The exciter E is driven at a constant speed by a suitable engine I6. To control the field excitation of the alternators I provide a source of constant potential evidenced by buses I8 and 20.

For normal cruising at normal speeds switch 22 is open and switch 24 closed. The generator excitation is thus controlled by resistor 21 and rhecstat 29.

During starting and maneuvering it is however 25 important to limit the torque on the Diesel engines. As is well known internal combustion engines and particularly Diesel engines have criti- `cal speed torque characteristics. A Diesel engine running if subjected to a torque above the criti- 3,ca1 point on its speed torque characteristic will stall. To prevent such stalling, it is imperative that the alternator excitation be decreased. To effect this decrease considerably more rapidly than the speed decrease of the alternator I provide the resistor having many sections. simplicity I have shown only five sections.

To separate points on this resistor 30, I connect a plurality kof resilient contact members 3|.

These contact members are mounted in a base For 0 32 of insulating material and at the free ends are arranged to successively contact the wedgeshaped block 33 of insulating material.

For the controlling eiect I wish to obtain, I provide such energization for the electromag- 5 netic device 34 that all or substantially all the resilient contact members 3| contact each other at 35 to thus shunt all or substantially all the `sections, of resistor 3D. Thus I accomplish by suitable selection of the compression spring 36 and suitable positioning cf pin 31 for an energization of coil 38 represented by the portion of ,the curve 48 (see Fig. 2) to the right of point 49. To effect the desired rapid decrease in the alternator excitation at the critical low speed of the engine I utilize a low pass filter circuit 40.

In this low-pass lterY circuit provide three adjustable reactors lil, ft2 and i3-one for each phaseand three adjustable capacitors ed, l5 and l6-one for each phase. It is not essential that three-phase reactors and three phase capacitors be used. A single phase low pass iilter may be used. There are, of course, some advantages in the use of three phase equipment. Among other advantages is the smoother and more uniform output. Ordinarily the adjustment of the reactors and the capacitors would be done at the factory so that attendants cannot alter the characteristics of the low pass filter circuit.

To obtain a direct current output voltage I utilize the three phase rectifier il?. The direct current output terminals of these rectifiers are connected to the coil 38. It is thus apparent coil 38 is energized proportional to the output voltage of the low pass lter circuit.

I so tune the circuit that coil 38 is energized substantially a constant amount for all frequencies, or speeds, falling to the right o point :39. As the frequency decreases the curve $8 gradually becomes curve lS' at region 53. At a speed represented by point t corresponding to the change from curve i8 to 33' at region 53, the energization of coil 38 suddenly rises. The armature 58 is thus moved clockwise and resilient contact members contact block 33 in so doing breaks the contacts at 35. The excitation of the exciter isV thusfdecreased rapidly with the result that the generator-excitation drops from curve 6| to l 62. overloading of the engines is thus prevented and no stallingwill take place. It is of course Vapparent that during these operations switch 2t must be open. 1

From the foregoing it will be apparent that I have provided a cheap and efficient means for preventing' the stalling of the engine or engines in ,the use at the low speeds.

I claim as my invention:

l. In a ship propulsion system, in combination, a Diesel engine, an alternator coupled to be driven by said Diesel engine, a low pass iilter circuit connected to the alternator output terminals, and

low pass filter circuit including adjustable reactors and adjustable capacitors and an output circuit, and low pass lter circuit being adjusted to have a relatively low constant output for all alternator frequencies above a given frequency but which exhibits a rapid rise in energy output as the alternator frequency is decreased below said given frequency, andV means responsive to the rapid rise of energy output of said low pass filter circuit for decreasing thefexcitation of said alternator to thus reduce the torque on said Diesel en-gine.

2. In a ship propulsion system, in combination, a conventional Diesel engine which, as is well known, may stall if subjected to an excessive torque at low speed, an alternator coupled to said Diesel engine, load means connected to said alternator, a iield winding for the alternator, a multistep adjustable resistor for varying the current in the eld Winding, electromagnetic means for adjusting the adjustable resistor, and means responsive to a given range of frequencies of the alternator for controlling the operation of said electromagnetic means.

3. In a ship propulsion system, in combination, a propeller driving `motor. an alternator connected to the motor for operating the motor, a variable speed prime mover coupled to drive the alternator to generate alternating current of varying frequency to alter the speed of the motor, said prime mover being of the type having a limited torque output at low speeds, a eld winding for the alternator, exciting means for exciting the alternator field winding, said exciting means including a circuit having a resistor included therein, a .plurality of contact members connected to separate points along said resistor, stop means for spacing the contact .members when engaging said stop means, electromagnetic means responsive to the vfrequency of the alternator and normally so energized by the alternator for al1 frequencies above a certain low frequency as to actuate said contact members awayfrom said stop means to thus maintain substantially allthe sections of said resistor short-circuited but when the alternator frequency drops to 'said certain low frequency releases said contact members to move against said stop means to thus successively remove the short circuit from sections of said resistor to thus decrease the iield excitation of the alternator, whereby the torque is decreased on the prime mover.

4. In a ship propulsion system, in combination, an alternator driven by a suitable variable speed prime mover, toV generate alternating cur- `rent of varying frequency, a low ,pass lter circuit including reactors, capacitors, and rectifiers connected to said alternator, the adjustment of said low pass lter circuit being such that the output voltage of the rectiflers remains substantially constant and at a relatively'low value for all alternator frequencies above a -given value but rises rapidly as the'alternatorfrequency drops below a certain value, and electromagnetic means for decreasing the field excitation substantially proportional to the output voltage of the rectifiers.

5. In a power system, in combination, an alternator driven by a suitable variable speedvprime mover, said alternator having a rleld winding, excitation control means for controlling Vthe excitation of said alternator, a low pass lter circuit connected to the alternator, means for Atuning the said filter circuit so as to produce a SIMON L. LINDBECK. 

